As is disclosed in, for example, JP, A No. 61-56015, JP, A(U) No. 59-68047, JP, A(U) No. 60-79919 and JP, A(U) No. 60-168325, a transmission for propelling a walking mower according to the prior art is, in general, fashioned such that it transmits power of an engine to left and right drive wheels without a speed-change control and only with a speed-reduction control.
A prior art transmission including a speed-change mechanism is known from JP, A(U) No. 61-135057. Although structure of the speed-change mechanism cannot be understood exactly from the specification and drawings of this laid-open application, it is believed that the change mechanism provides only few variable speeds, such as two variable speeds, of a walking mower.
The reason why a transmission for walking mowers has been fashioned to have no speed-change mechanism or to have a speed-change mechanism providing only few variable speeds, as described above, is that a compactness of the transmission is to be secured so as to eliminate a limitation against the arrangement of a mowing cutter and so as not to sacrifice a compactness of the whole of a mower. It is believed, however, very convenient if speed of a walking mower could be selected from a plurality of variable speeds in accordance with height and/or density of turfs, operator's liking and so on. Further, it is wished to travel a walking mower with a relatively high speed when the mower is not used for mowing and is merely travelled.